A radar device, which is an example of a conventional object detection device, transmits an electromagnetic wave forward of a vehicle and performs signal processing on a reflected wave from an obstruction (object) located forward of the vehicle to detect the presence of the obstruction and measure a distance to the obstruction (see, for example, Patent Literature 1). This radar device includes a radar tilt detection means and a vehicle tilt detection means. The radar tilt detection means detects a tilt of the radar device with respect to a direction perpendicular to a running surface of the vehicle. The vehicle tilt detection means detects a tilt of the vehicle with respect to the direction perpendicular to the running surface. If a relationship between the tilt of the radar device detected by the radar tilt detection means and the tilt of the vehicle detected by the vehicle tilt detection means is shifted from an initial relationship, the radar device determines that an off-axis of the radar device occurs in the perpendicular direction.